April 2016 is a long time from now. I would expect multiple schedule changes between now and then, and possibly an equipment change. Even if they move to a plane without lie-flat seats, they may move back to one with them. I would wait and see what it looks like a few months before your flight before worrying.
What will you do if UA drops lie-flat seats from HI all together? Are you OK with non-lie-flat seats from LAX or SFO?